Amid the torrent of stories about the shocking new revelations about the National Security Agency, few have bothered to ask a central question. Who’s actually doing the work of analyzing all the data, metadata and personal information pouring into the agency from Verizon and nine key Internet service providers for its ever-expanding surveillance of American citizens?

Over the past decade, the U.S. intelligence community has relied increasingly on the technical expertise of private firms such as Booz Allen, SAIC, the Boeing subsidiary Narus and Northrop Grumman. About 70 percent of the national intelligence budget is now spent on the private sector. Former NSA Director Michael V. Hayden has described these firms as a quote “digital Blackwater.” We speak to Tim Shorrock, author of the book “Spies for Hire: The Secret World of Outsourced Intelligence.”